1. Field of the Invention
This invention relates to heat fixing rolls for use in plain paper copiers (PPC), laser beam printers (LBP), and facsimile machines and more particularly, to low-hardness silicone rubber fixing rolls having a silicone rubber layer on a mandrel and an organic resin layer having a low surface energy thereon.
2. Background Art
Fixing rolls having a silicone rubber layer on the outer surface of a metal mandrel and a fluoroplastic resin layer or fluoroplastic latex layer thereon are often used in various business machines such as copiers, laser beam printers, and facsimile machines because the resin layer has superior toner release properties. With the recent speedup of copiers, laser beam printers, and facsimile machines, the fixing device is required to insure a sufficient fixing width or nip width to increase the time taken for fixation. To this end, attempts have been made to reduce the hardness of rubber material to a level unmeasurable with a JIS hardness meter. However, although the rubber material on the fixing roll is made thin, an appropriate nip width is not obtained even under a low nip pressure because of the high resilience of rubber.
Low-hardness rolls at a hardness level unmeasurable with a JIS hardness meter have the problem that the durable adhesion of fluoro-resin covering the outer surface of silicone rubber is adversely affected if silicone rubber experiences substantial hardness variations under different curing conditions (primary vulcanization conditions).